In the field of web products, when it is necessary to carry out an operation according to a determined pitch, such as a perforating, punching, stamping or stitching operation, it is sometimes necessary to have great precision in positioning the tool carrying out the desired operation.
Thus, in the patent application filed on 17 Sep. 1992 by the applicant and Jacques F. Gaudillat, Ser. No. 7/927,502, entitled "Process and Device for Driving a Surface in a Reciprocating Motion in a Given Plane", a description is given of a device for carrying out an operation, according to a given pitch, on a web movable uniformly and continuously. The device comprises a first block fitted with a tool describing, in an reciprocating manner, a short portion of an arc of a circle around a stationary horizontal axis parallel to the movement axis of the web, in order to be able to make the tool cooperate periodically with a member complementary to the tool. The complementary member is provided on a second block, the first block being connected to the second block along the stationary axis. The two blocks are fixed and suspended in this way to a stationary frame and are driven parallel to the movement plane of the web by a reciprocating movement of greater magnitude than the movement of the first block around the stationary axis and of identical period.
For this type of device, particularly when applied to perforating, it is essential that there is no translation movement, in the movement plane of the web, of the blocks in relation to each other.
In the previous technique, it is common to make use of mechanisms of the "SCOTT-RUSSEL" type, which will be described in greater detail in the description which follows and which include a number of joints, pivots or slides. These mechanisms undergo fairly rapid wear, which causes increasing inaccuracies in the positioning of the tool. Furthermore, it is difficult to use such mechanisms when the second plane (i.e, the short portion of an arc of a circle) is not exactly perpendicular to the first plane (i.e. the plane of the web). Such a mechanism is described, for example, in U.S. Pat. No. 3,102,721.